The procedure was described to Rapoport as a "minor cleanup." The 6-foot-7, 292-pound Armstead should be cleared for most, if not all of the team's spring drills. Armstead said on KHTK-AM in Sacramento that he will be back for organized team activities.

Entering his fourth season, Armstead notched 1.5 sacks last season and played well against the run before winding up on injured reserve with a broken hand. The 24-year-old lineman landed on injured reserve the previous campaign, too, with a shoulder injury that required offseason surgery.

The Niners believe enough in Armstead to have picked up his fifth-year option in April. Limited to 14 games over the past two years, though, the former first-round pick is under pressure to put together a full season in 2018.